Chemically toughenable lithium-containing borosilicate glass, for ophthalmic lenses, has high sodium, lanthanum, niobium and titanium oxide contents and a low calcium oxide content

摘要

A chemically toughenable lithium-containing borosilicate glass, having high sodium, lanthanum, niobium and titanium oxide contents and a low calcium oxide content. A novel glass has the composition (by wt., on oxide basis) 33-37% SiO2, 7.5-13% B2O3, 5-8% Li2O, greater than 2.5-7.5% Na2O, 0-2% K2O, 0 to less than 8% CaO, 0-6% Al2O3, 8-13% Nb2O5, 4-6% ZrO2, 5-10% TiO2, 12-19% La2O3, 2-4% SrO and 0-0.8% As2O3 and/or Sb2O3 refiner, the sum of SiO2 + B2O3 being 44-48% and the sum of Li2O + Na2O + K2O being less than 14%. Independent claims are also included for the following: (i) a surface toughened glass comprising the above glass with a compressive surface layer; (ii) ophthalmic lenses of the above glass; and (iii) production of the above surface toughened glass by chemical toughening of the above glass.